A variety of interbody fusion implants exist for replacing damaged spinal disc segments of the human body. The interbody fusion implant is used to replace a deformed, injured or diseased natural intervertebral disc. An interbody fusion implant connects two adjacent vertebrae together, retains the vertebrae in the correct position, and limits their relative movement such that the adjacent vertebra and the implant fuse together.
There are various accepted procedures for installing intervertebral fusion implants or cages between adjacent lumbar vertebrae, such as, the posterior approach and the anterior approach. In the posterior approach, a surgeon makes an incision along the back of the patient. The surgeon moves the spinal muscles and nerve bundles, which are close to the surface of the back, to access the diseased disc. The diseased disc is replaced with an interbody fusion implant or cage. This is commonly referred to as a “posterior lumbar interbody fusion” (PLIF).
In the anterior approach (meaning from the front of the patient), a surgeon makes an incision in the abdomen of the patient. With the aide of one or more surgical instruments, the surgeon reaches through the chest cavity to access the damaged vertebral disc and replace it with the interbody fusion implant. This is commonly referred to as “anterior lumbar interbody fusion” (ALIF). The invention disclosed herein is particularly useful for ALIF procedures, but could also be useful for a PLIF procedure with minor modifications.
An ALIF distractor is shown and described in U.S. Pat. No. 7,118,580 to Beyersdorff et al. This reference discloses an ALIF distractor for installing a three-piece artificial disc between adjacent vertebral bodies. The three-piece artificial disc comprises an upper part for placement against a first vertebral body, a lower part for placement against an adjacent lower vertebrae, and a pivot element that can be inserted between the upper and lower parts. The insertion instrument comprises two elongated arms, disposed side by side and pivotably supported relative to one another. A retention pin is positioned at the end of each elongated arm, whereby the retention pins are inserted into bores provided in the upper part and the lower part of the intervertebral implant. A thrust guide is positioned between the arms of the insertion instrument for inserting the pivot element between the upper part and the lower part of the artificial disc.
In practice, the upper and lower parts of the artificial disc are first installed on adjacent vertebrae. Thereafter, the thrust guide is slid between the arms of the insertion instrument, spreading apart the elongated arms and the adjacent vertebrae. The pivot element of the artificial disc is pushed between the upper part and the lower part of the artificial disc by the thrust guide. After the pivot element is set in place, the thrust guide is retracted thereby contracting the arms and closing the large gap between the adjacent vertebrae. The pivot element is then captivated between the upper part and the lower part of the artificial disc.
The ALIF distractor of '580 is tailored for use with a three-piece intervertebral disc implant. Because other types of disc implants and fusion implants exist, such as a one piece fusion implant, there remains a need for alternative ALIF distractors. Furthermore, despite existing ALIF distractors, there remains a need to provide an ALIF distractor to facilitate the proper and convenient insertion of an fusion implant between adjacent vertebral bodies using the ALIF surgical technique while minimizing the risk of injury to the patient.